The FunctionWrapper

The CommandAPI includes the FunctionWrapper class which is a wrapper for Minecraft's functions. It allows you to execute the commands that are represented by the respective .mcfunction file.

The FunctionWrapper class is an extension of the SimpleFunctionWrapper class. It is a SimpleFunctionWrapper which has been constructed from an existing command sender when a command is used. This means that the command sender has already been "baked into" the FunctionWrapper object, allowing you to run it without having to provide a command sender.

FunctionWrapper methods

The FunctionWrapper class has the following methods:

class FunctionWrapper extends SimpleFunctionWrapper {

    // Methods specific to this class
    int run();
    int runAs(Entity e);

    // Methods inherited from SimpleFunctionWrapper
    static SimpleFunctionWrapper getFunction(NamespacedKey key);
    static SimpleFunctionWrapper[] getTag(NamespacedKey key);
    static Set<NamespacedKey> getFunctions();
    static Set<NamespacedKey> getTags();
    int run(CommandSender sender);
    String[] getCommands();
    NamespacedKey getKey();
}

These methods allow you to interact with the Minecraft function that this class wraps.

run()

The run() method runs the function. The command executor that runs this function is the command executor that was used to retrieve it. For example, if a player in-game populated this argument, then the player will be filled in for @p and the player's location would be used for things such as ~ ~ ~:

new CommandAPICommand("runfunc")
    .withArguments(new FunctionArgument("function"))
    .executes((sender, args) -> {
        FunctionWrapper[] functions = (FunctionWrapper[]) args[0];
        for(FunctionWrapper function : functions) {
            function.run(); // The command executor in this case is 'sender'
        }
    })
    .register();

runAs(Entity)

The runAs(Entity) is the same as the run() method, but it allows you to change the command executor to another entity.